What inverter for Solyndra

ZoNiE
ZoNiE Solar Expert Posts: 100 ✭✭
in Solar Beginners Corner #1
I have three Solyndra panels. 200 series. 173W. One has one broken tube, so a few fewer watts on that one.

I want to use them on a trailer, maybe all of them, maybe only two. Usually they are grouped four in series in a 600V system, and then the typical small array is 6 groups for 24 total panels. There are plenty of 5KW inverters out there that work for this.

In my case, I am looking at around 500 rated watts, so I really need a smaller inverter. The most I would ever consider adding to this is probably one more panel due to space, so any inverter under 1KW will do fine. They are parallel tubes so one could conceivably cut the side bars and shorten a panel to fit in a tight spot, hence the reason I want to parallel them.

The Vmp on these should be around 80V (I say should be because the 200 series data sheet only shows 182-220W panels, so I am calculating these values based on the steps between the other sizes 182, 191, 200, etc...)

The Voc is about 117V.

I'm more inclined to parallel these also so I don't have the issues with arc since this is a vehicle, and things move. I don't like High DC voltage on anything.

What should I be looking for in a micro (or mini) inverter? Who makes something I can use? I looked at the systems at Intersolar last week, but most were for large arrays, 5KW and up.

Is there a good small charge controller/charger that will act more of a DC-DC buck so I can connect it to the DC system in my coach? I only really want it to keep the 2 GC2's (maybe four eventually) topped up and run the usual 12V loads. I have a genset for the Microwave and the Air conditioner when I need those.

I'm really just looking for a low cost way to use some of the stuff I got basically for free, and learn more about using and living with minimal solar, and maximizing my charging and energy output before I invest in a larger system for my home.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: What inverter for Solyndra

    You've got some things confused I think.

    The kind of inverters that connect directly to solar panels are grid-tie inverters, and they only work with a stable AC power source to sync to. This is not going to work in a mobile application.

    Therefor the inverter size is irrelevant, as you should be running these through an MPPT charge controller to keep some batteries up. With a Voc of 117 you need at least a 150 Volt input controller, and even then you could run into trouble with cold temps raising the Voc. MidNite Classic 150 with its HyperVoc function would be minimum if you experience sub-freezing temperatures.

    On a 12 Volt system the down-conversion efficiency won't be at its best from 80 Vmp, but it will work. Three 173 Watt panels is 519 Watts which would make peak current around 33 Amps on a 12 Volt system. Definitely enough to keep up a set of GC2's, and then some.

    As for the one broken one having slightly lower output, have you actually tested it?
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  • ZoNiE
    ZoNiE Solar Expert Posts: 100 ✭✭
    #3
    Re: What inverter for Solyndra

    I have not tested any of them yet, waiting for cooler weather to screw around with them, but the tubes are all in parallel so one less should equate to reduction by the amount the individual tube generates.

    I should have been more clear on the inverter part. I have been looking at one that will run sans grid as well. I'm waiting for a response from the mfg on whether or not I can use it the way I think I can.

    I had also thought about using one on the trailer and the other two at home to run the jacuzzi pump, so a small inverter would be needed.

    I only recently started looking at MPP controllers since I cannot find what I need for the panels for AC use at such a low wattage. Thanks for the info, I just now looked at those.

    The voltage ratings are confusing. What voltage do I shop on, Voc or Vmp? I was told Voc. I don't think freezing temps will be a problem. I'm in Arizona and I don't generally camp in sub Z weather. Soo, if the panels and batteries are coooooold, then the Voc could go higher? The midnite Kid, has protection for over 150, but I don't think I'd ever see that high a voltage.

    How did you arrive at your Ampacity of 33A? 519/12=43.25 RMS conversion? 15.7V charge voltage?

    I also have a really nice Sensata DImensions 2200W inverter, but it needs 24VDC input, so I need to decide If I want to go 24V or sell it and get something smaller and 12V.



    Decisions, decisions...
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: What inverter for Solyndra
    ZoNiE wrote: »
    The voltage ratings are confusing. What voltage do I shop on, Voc or Vmp? I was told Voc. I don't think freezing temps will be a problem. I'm in Arizona and I don't generally camp in sub Z weather. Soo, if the panels and batteries are coooooold, then the Voc could go higher? The midnite Kid, has protection for over 150, but I don't think I'd ever see that high a voltage.

    Both Voltage are important to picking a charge controller. These panels are not going to run a GTI at 80 or 160 Volts; there are no good grid-tie inverters that operate in that range nor would it be legal or advisable to hook up a GTI without the proper procedures.

    Voc matters for maximum input Voltage. If the panels hit 117 Volts then the controller must be able to take more than that. I mention the cold temperature effect because up here that 117 would hit 152 Volts and the only controller that would handle it is the Classic (aside from the 600 Volt specialty units).

    Vmp matter because it is the peak operating Voltage under load (Voltage at maximum power). This affects the controller's conversion efficiency. Thus 80 Vmp would be more efficient on a 48 Volt system because there is not as much down-converting of Voltage into current. For a 12 Volt system you're probably losing 5% of the available power to that adjustment.
    How did you arrive at your Ampacity of 33A? 519/12=43.25 RMS conversion? 15.7V charge voltage?

    Peak charge current: Array Watts * 77% typical efficiency / nominal system Voltage. So with all the panels together at 519 Watts * 0.77 / 12 Volts = 33 Amps. If you are going to use only two of the panels the result would be 22 Amps. The MidNite Kid would handle either, providing the panels never get cold, but will 'clip' a bit of power if all three are used (and capable of maximum power).
    I also have a really nice Sensata DImensions 2200W inverter, but it needs 24VDC input, so I need to decide If I want to go 24V or sell it and get something smaller and 12V.



    Decisions, decisions...

    Always decisions. Inevitably you have multiple options before you and you have to pick one based on some criterion. Sometimes it's not easy to decide which, other times the choice is obvious.
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  • ZoNiE
    ZoNiE Solar Expert Posts: 100 ✭✭
    #5
    Re: What inverter for Solyndra

    Thanks for the quick response. Gotcha on the 77%. I knew it had to be something relating to efficiency or some conversion related to solar and not general electrical engineering, as RMS conversion didn't quite give me that number.

    I am looking at the Kid now as the ideal unit since the smaller system will also have less loss. The 30A pretty much matches the charger/converter in the RV. I can always add a second one if I grow this system. Outback seems to have a good track history, although looking at the Kid's manual, it appears it has some other brand on it in the diagrams as if they bought the IP from some entity called "marco".
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #6
    Re: What inverter for Solyndra

    Hi ZoNiE,

    "Mario" is the Design Engineer of the KID, AT MidNIte Solar.
    In answer to a question asked elsewhere, I believe that the KID Beta program ended some months ago.

    As you probably know, wind-sun is selling them:
    http://www.solar-electric.com/inverters-controllers-accessories/chco/misoclchco/midnite-solar-kid-mppt-charge-controller.html

    And, FWIW, the KID also has HyperVOC to 162 VDC input.
    Have Fun Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • ZoNiE
    ZoNiE Solar Expert Posts: 100 ✭✭
    #7
    Re: What inverter for Solyndra

    Thanks Vic. I have been absorbing the info on the other forum and yeah, figured out the Mario thing just after I posted it. Seems that Midnight stuff seems to be the culmination of all the experts who banded together to make their own way instead of making it for others. Been there, done that. A good thing.

    I also found the prices on this site to be pretty good. Gonna look into what I want to buy over the next couple of weeks.
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